Birth delivery mode modifies the associations between prenatal polychlorinated biphenyl (PCB) and polybrominated diphenyl ether (PBDE) and neonatal thyroid hormone levels.
BACKGROUND
Developing infants may be especially sensitive to hormone disruption from chemicals including polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs).


OBJECTIVE
We investigated relationships between cord serum levels of PCBs and PBDEs and thyroid hormones measured in cord blood serum and neonatal blood spots.


METHODS
We measured PCBs and PBDEs, thyrotropin (TSH), thyroxine (T4) and free T4 (FT4) in cord blood serum from 297 infants who were delivered at the Johns Hopkins Hospital in 2004-2005. We abstracted results of total T4 (TT4) measured in blood spots collected in the hospital and at neonatal visits. We used delivery mode (augmented vaginal deliveries and nonelective cesarean deliveries) as a surrogate for intrapartum stress, which is known to alter cord blood thyroid hormones.


RESULTS
In the full study population, no compounds were associated with a change in average TSH, FT4, or TT4. BDE-100 was associated with increased odds of low cord TT4, BDE-153 with increased odds of low cord TT4 and FT4, and no compounds were associated with increased odds of high TSH. For infants born by spontaneous, vaginal, unassisted deliveries, PCBs were associated with lower cord TT4 and FT4 and lower TT4 measured in neonatal blood spots. PBDEs showed consistent but mainly nonsignificant negative associations with TT4 and FT4 measurements.


CONCLUSIONS
Prenatal PCB and PBDE exposures were associated with reduced TT4 and FT4 levels among infants born by spontaneous, unassisted vaginal delivery. Intrapartum stress associated with delivery mode may mask hormonal effects of PCBs and PBDEs.
Herbstman
Julie B
JB
Columbia Center for Children's Environmental Health, Department of Environmental Health Sciences, Columbia Mailman School of Public Health, New York, New York 10032, USA. jh2678@columbia.edu
Sjödin
Andreas
A
Apelberg
Benjamin J
BJ
Witter
Frank R
FR
Halden
Rolf U
RU
Patterson
Donald G
DG
Panny
Susan R
SR
Needham
Larry L
LL
Goldman
Lynn R
LR
D000328:Adult; D036861:Delivery, Obstetric / Q000379:methods*; D004781:Environmental Exposure; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D018811:Maternal Exposure; D011075:Polybrominated Biphenyls / Q000633:toxicity*; D011078:Polychlorinated Biphenyls / Q000633:toxicity*; D011247:Pregnancy; D013963:Thyroid Hormones / Q000097:blood*
D011075:Polybrominated Biphenyls; D013963:Thyroid Hormones; D011078:Polychlorinated Biphenyls